Spark plug with automatic means for varying its heat dissipation capacity



rqbb HwwfA M W INVENTOR I'M ATTORNEYS H. W- ANDERSEN SPARK PLUG WITH AUTOMATIC MEANS FOR VARYING Filed Feb. 23, 1961 ITS HEAT DISSIPATION CAPACITY April 21, 1964 L III.

United States Patent 3,136,338 SPARK PLUG WITH AUTOMATIC NEANS FGR VARYWG iTS HEAT DESSIPATION CAPACITY Harold W. Andersen, 532 Manhasset Woods Road, Manhasset, N.Y. Filed Feb. 23, 196i, Ser. No. erase 3 Claims. (63. 313-115) This invention relates to a spark plug for internal combustion engines, and has for an object to provide such a plug which embodies automatic means for varying its conductive capacity for dissipation of heat according to changes in temperature within the cylinder or cylinders of the engine due, for example, to increase and decrease in the rotative speed of the engine crank shaft arising from acceleration and deceleration of the speed of travel of the vehicle in which the engine is installed.

Another object is to provide such a means which is constituted by an element so positioned in the spark plug structure that it is normally, or at relatively low cylinder temperature, out of heat contact relationship with the base or shell of the plug, while adapted automatically to make such contact upon increase in said temperature beyond a predetermined degree, and then return to lowheat conducting relationship upon subsidence of or reduction in the temperature.

Another object is to provide such a means in which the just named element is composed of a bimetal, one component of which has a higher coefficient of linear expansion under the influence of heat than the other component, whereby increase in attendant heat will cause the component having the higher coeflicient of expansion to distort the other component and establish the heat conducting contact desired in the presence of elevated temperature, while reduction in temperature Will cause the element to return to its original form, out of heat conducting contact with the base or shell of the plug.

Another object consists in providing such a means in which the above described element is a cup shaped sleeve that is slit to form a series of fingers which are united at the base and are free to expand radially outward; the component of the bimetal having the greater coefiicient of linear expansion being on the inside of the sleeve; and the element itself being designed and adapted to seat within the base or shell of the plug without requiring substantial change in the design or size of what may be regarded as a standard form of spark plug.

Another object consists in providing an adjustable air gap between the crown of the plug, with its terminal connection for the source of electric current, and the upper end of the central electrode or conductor of the plug, which air gap serves to increase the intensity or voltage of the current fed to the said electrode or conductor, thereby varying the intensity of the ignition spark within the engine cylinder.

A further object consists in providing certain improvements in the form, construction, arrangement and material of the several parts, whereby the above named objects and others inherent in the invention may be efiiciently attained.

It is well known by those familiar with this industry that spark plugs for internal combustion engines normally comprise a main electrode or conductor substantially axially disposed within an insulating body or core, the latter being carried in a base or shell composed of conductive metfl, such as steel, to the lower or inner portion of which base or shell is atfixed the grounding electrode that is so located as to establish a spark gap between it and the inner end of the main electrode. An appropriate heat conducting and sealing member such, for instance, as a copper washer or gasket, is normally interposed between the insulating core and the base or shell of the plug 3,139,333 Fatented Apr. 21, 1964 for the dissipation of heat of combustion through the base or shell and to the engine block into which the spark plug is threaded.

it is also recognized that the temperature within the combustion chamber of the engine increases with speed of crank shaft rotation such as normally takes place with acceleration in travel of the vehicle in which the engine is mounted; and this fact or phenomenon has been found to be very pronounced in the case of certain classes or types of vehicles .such as the small domestic and foreign automobiles which are now rapidly increasing in numbers. There has arisen a difficulty in this last connection due to the fact that spark plugs in common usage do not embody sufiicient conductive capacity for heat dissipation to accommodate the increase in temperature of combustion just explained, with the disadvantageous or objectionable result of malfunctioning by and/ or injury to the engine arising chiefly from such elevation in temperature of the spark plug base or shell [as to cause pre-ignition of the combustion charge within the cylinder and knocking or pounding in engine operation. The present invention is calculated to eliminate this difficulty by providing means for automatically increasing heat dissipation through conductivity when the temperature of combustion reaches a predetermined degree, and reducing the conductivity and heat dissipation as the combustion temperature recedes to a lower degree.

In a brief summary, the invention consists in positioning within the conducting base or shell of the plug an element composed of bimetal, e.g. nickel and steel, which has normally only limited contact with the base or shell but is designed and adapted to be deformed under the influence of elevated temperature to establish additional thermal contacts therewith, and likewise to return to its limited contact form upon lowering of combustion temperature. The said element preferably consists of a cup shaped sleeve which is slit to form upstanding fingers, the inner layer or component of which has a greater coeriicient of linear expansion than the outer layer or component; whereby elevated temperature resulting from combustion acts upon the said fingers to distort or bend them outwardly into contact with the plug base or shell and greatly increase the total capacity of the plug for heat dissipation. Upon lowering of the temperature, the shrinkage of the inner layer or component of the birnetal fingers will restore them to their normal position out of contact with the plug base or shell. The bimetal of which the element is composed is preferably a composition of nickel and steel and known as thermal metal, but other compositions adapted to the functional action just described may be substituted.

Practical embodiments of the invention are represented in the accompanying drawing; in which:

FIG. 1 represents a longitudinal central section, partly in elevation, of the assembled spark plug;

FIG. 2 represents a detail view, in elevation, of the upper or outer portion of the plug;

PEG. 3 represents a transverse section on the line III III of FIG. 1;

FIG. 4 represents a perspective view of the thermal bimetal conducting element in normal shape;

FIG. 5a represents a detail view of part of said element when distorted or expanded under the influence of heat without restriction; and

FIG. 5!) represents, somewhat diagrammatically, a detail view of part of the said element expanded against the adjacent inner wall of the shell.

Referring specifically to the showing of the drawings, the spark plug comprises a base or shell 1, preferably composed of a ferrous metal, such as steel, and provided at its lower portion with an exterior thread 2 for screwing the 3 a plug in a cylinder of an engine, and at its upper portion with a hexangular flange 3 for tool operation.

The body or core of the plug, denoted generally by 4 is, as usual, composed of any suitable insulating material such, for instance, as a ceramic containing suitably treated aluminum oxide.

The main electrode or conductor is denoted by 5 and, as is the general practice, it is set axially within the core 4 with its lower extremity, marked 6, projecting from the tapering inner end of the core 4 and forming a spark gap between it and the grounding electrode or conductor 7 that is fixed to the lower edge of the base or shell 1.

Within the base or shell is a slanting shoulder 8 against which is seated a washer or gasket 9 of copper or the like for the dual purpose of forming a gas-tight seal, and aiding in the dissipation of heat of combustion by providing a conductive path between the core 4 and the base or shell which, in turn, has thermal contact with the engine block.

Characteristic of the present invention is the provision of an element in the form of a cup shaped sleeve which has a lower portion 19 adapted to seat tightly in the washer 9, and a generally cylindrical side wall projectitng upwardly from the said portion 10 said side wall being slit to form a plurality of strips or fingers, a few of which are indicated by the reference numeral 11. This element is of such size as to be housed within the upper part 12 of the base or shell 1, leaving a small air space therebetween, which space may be, for instance, about five one-thousandths to eight one-thousandths of an inch (.G05"" A bimetal material such, for instance, as a composite of nickel and steel alloys, is used for the element 16, ll. It may be fabricated into the shape shown and described by any suitable procedure, all of which is well within the knowledge and understanding of operatives in this field, and the arrangement of material is such that the nickel alloy, or the like, component is on the inside of the element 1! 11, with the steel alloy component, or the like, on the outside. A ring or a gland nut 13 is threaded into the said part 12 of the base or shell and abuts a shoulder 14 on the core 4 (preferably with the interposition of a brass or bronze split ring 9' serving as a cushion) so as to force the core down and grip the portion 10 tightly between the core and the gasket 9, thus also maintaining the elements of the plug in assembled relation.

Within the open upper or outer end of the body 4 is threaded the usual hollow crown element 15 that is composed of suitable electric conducting material such, for instance, as steel, and carries a terminal post 16 for attachment of a wire, or the like (not shown), leading from a source of electric current.

Another feature of the present invention resides in constructing the upper or outer end of the spark plug so that, if desired, an air gap of greater or less extent may be provided between the crown l5 and the end of the main electrode 5, for varying the eifective voltage of the supplied current. To accomplish this I insert a wire connector, in the shape of part of a spring, one portion of the connector denoted by 17, being permanently and resiliently seated in a groove within the lower portion of the crown 15, as clearly shown in FIGS. 1 and 3, while another portion, 18, extends from the said groove through a slotted aperture 19 formed in the side of the crown is, which aperture has three notches indicated by 20, 21 and 22. The notches 28, 21, 22 may be calibrated to provide gap settings of .010, .026 and .030, for instance.

It will be understood that the portion 18 of the connector has a resilient tendency to press downwardly so that, when its extremity is in the lower end of the aperture H, the said portion 18 will rest upon the end or top of the main electrode 5. If, now, it is desired to provide an air gap between the said portion 13 (and hence the crown l5) and the electrode 5, the extremity of 18 is lifted and seated in notch 25 Similar removal to the notch 21, or the notch 22, will increase the air gap and, likewise, increase the elfective voltage of the current passing through the plug and establislr'ng a spark gap at 6, 7, within the engine cylinder. The portion 17 can slide in its groove to accommodate itself to the lateral angular movement of the portion 13 in the course of such adjustments. Such an increase in effective voltage, with added intensity of the spark, is of advantage particularly in preventing or delaying fouling of the plug through carbonizing.

It is believed that the manner of assembling the elements of the plug will be apparent from the foregoing description, but it may be pertinent briefiy to say that the gasket 9 is seated within the shell 1, and the element 19, 11, is then dropped in place on the gasket. The core 4 of the plug is inserted into the position indicated in FIG. 1 and fixed in place by screwing down the gland or ring nut 13. Finally, the crown 15, with its associated parts, is screwed into the upper or outer end of the insulator 4 either before or after the latter is assembled. This immediately foregoing description is merely intended as one way in which the parts may be assembled, and it will be understood that actual practice may resort to variations as desired; the manner of assembly constituting no part of the present invention.

In operation of the engine at lower speeds the heat of combustion will flow through the lower tapered portion of the core 4, through the copper (or other alloy) gasket 9 and the base or shell 1 of the plug with which the washer is in contact, and thence into the engine block for dissipation. Up to a certain point the outward bending movement of the bimetal fingers 11 will be negligible or at least insufficient to bring their free ends into contact with the portion 12 of the shell. At higher engine speeds, which normally follow vehicle acceleration or extended low-gear operation, for instance, the heat of combustion will become more intense and, when it reaches a predetermined suificiently high degree, the relatively greater expansion of the nickel alloy components of the element til, 11, will cause the fingers 11 to bend outwardly, as indicated (with some exaggeration) in FIG. 5b until the steel alloy components make thermal contact with the inside of the portion 12 of the base or shell 1, thereby multiplying the paths of thermal conductivity and greatly facilitating the dissipation of the excess heat through the shell 1 and into the engine block. Upon decrease in heat of combustion, following slower engine operation, the fingers 11 will shrink, so to speak, back to normal form out of contact with the base or shell of the plug.

By varying the composition of the metal alloy in gasket 9 from copper (high heat conduction) to silicon bronze (low heat conduction) various basic heat ranges can be accomplished with the same insulator or core and each such basic range can be extended considerably by the provision of the element ll), 11.

Thus, it will be seen that this feature of the present invention provides for regulating the eifective conductivity of the plug for dissipation of heat of combustion in a manner which is entirely automatic and which conforms to the temperature conditions within the combustion chamber or cylinder of the engine.

Adverting to the current adjusting feature at the outer end of the plug, it is deemed sufiicient to say that, whenever operating conditions call for an increase of effective voltage to prevent or delay fouling, as by carbonization, or for any other reason, an air gap of adjustable dimension may be established between the crown 15 with its terminal post 16 and the electrode 5 by moving the portion it; of the connector l7, 18, into any desired position within the aperture 19, i.e., into any one of the notches 2h, 21, 22.

The invention, accordingly, presents a spark plug which is substantially of normal size and appearance, but which is highly effective in conforming to different demands and conditions of use by automatically adapting itself to changes in combustion temperature and thereby obviating malfunction or misfunction, chiefly through pre-ignition; and by permitting adjustment for varying the efiective voltage passing through the plug from the source of electric current in order to maintain a reliable and efiicient ignition spark. It may be added that, if occasion should require, the element 1 9, 11 may easily be removed and replaced by a new one, and it may also be noted that the voltage adjustment device is located at a highly accessible place for easy and instantaneous setting whenever needed.

It will be understood that various changes may be resorted to in the form, construction, material and arrangement of the several parts of the plug without departing from the spirit or scope of the invention, and hence I do not intend to be limited to the details herein shown or described except as the same are included in the claims or may be required by disclosures of the prior art.

What I claim is:

l. A spark plug designed and adapted for internal cornbustion engines and embodying means for automatically varying the conductive capacity of its shell for dissipation of heat therethrough according to changes in combustion temperature within the engine, said plug comprising, a shell of heat conducting material adapted to be operatively fitted into a cylinder of the engine and carrying a grounding electrode, an insulating core within the shell, a conductor within said core carrying an electrode adapted to form a spark gap between it and the grounding electrode, and a solid heat conductive element in the form of a cup shaped sleeve surrounding the core and seated within but out of contact with the upper portion of the shell to leave an air space between its side wall and the shell, the said element being composed of a substance that is distortable by temperature and the side wall of which is adapted to bend outward laterally into thermal contact with the shell upon rise in temperature above a predetermined de ree and return to its original form out of contact with the shell upon fall below said degree thus increasing and decreasing the capacity of the shell for dissipating heat of combustion.

2. A spark plug as defined in clairn 1, in which the conductive element is composed of a bimetal of which one component has a greater coefficient of linear expansion than the othear and is on the inside of the side wall of the said element to cause outward and inward distortion upon rise and fall in affecting temperature.

3. A spark plug as defined in claim 2, in which the side wall of the conductive element is vertically slit at a plurality of points to form a circle of upstanding fingers united at their lower portions in a continuous bottom, the bimetal component on the inside of the fingers which has the greater coefiicient of linear expansion under the influence of heat serving to bend or distort the fingers laterally outwardly when the combustion temperature reaches a predetermined high degree to establish heat dissipating contact of the fingers with the shell of the plug and to shrink out of contact with the shell when the said temperature falls below the said degree.

4. A spark plug as defined in claim 3, in which the shell has an interior shoulder that supports the bottom of the conductive element, and which also includes a gasket of heat conductive material interposed between the said shoulder and the bottom of the conductive element to serve the double purpose of establishing a gas tight seal and also providing a heat dissipating path bety een the insulating core and the shell regardless of whether or not the fingers on the conductive element are in contact with the shell.

5. A spark plug designed and adapted for internal combustion engines comprising, a hollow heat conducting metallic shell having a reduced lower end and an enlarged hollow circular upper portion connected with the lower end by a shoulder and being interiorly threaded at the top thereof, a threaded ring nut mating with said threaded top, an insulating core within the shell having a circular enlarged portion positioned within the said enlarged upper portion of the shell, and a solid circular heat conductive element surrounding said enlarged portion of the core but spaced from the shell, said element consisting of a continuous lower portion and an interrupted side wall uprising therefrom constituted by a ring of separate fingers composed of a bimetal having components difiering in their coefiicient of linear expansion under the influence of heat with the component having the higher coefficient on the inside of the fingers.

6. A spark plug as defined in claim 5, in which the shoulder connecting the lower end and upper portion of the shell slants and the lower portion of the conductive element is shaped to mate with said shoulder.

7. A spark plug as defined in claim 6, which also includes a heat conducting gasket between said shoulder and said lower portion of the conductive element.

8. A spark plug as defined in claim 7, in which the enlarged portion of the core has an upper shoulder apadted to mate with the said ring nut and screwing of the latter firmly assembles the core in the shell and also defines the operative position of the said conductive element.

References Cited in the file of this patent UNITED STATES PATENTS 984,454 Thwaite Feb. 14, 1911 1,343,052 Heath June 8, 1920 1,355,427 Riggs Oct. 12, 1920 1,415,447 Howard May 9, 1922 1,935,862 Tebaldi Nov. 21, 1933 2,208,708 Sprague July 23, 1940 2,212,725 Andres Aug. 27, 1940 2,241,240 Chirelstein May 6, 1941 FOREIGN PATENTS 5,467 Australia Dec. 21, 1931 

1. A SPARK PLUG DESIGNED AND ADAPTED FOR INTERNAL COMBUSTION ENGINES AND EMBODYING MEANS FOR AUTOMATICALLY VARYING THE CONDUCTIVE CAPACITY OF ITS SHELL FOR DISSIPATION OF HEAT THERETHROUGH ACCORDING TO CHANGES IN COMBUSTION TEMPERATURE WITHIN THE ENGINE, SAID PLUG COMPRISING, A SHELL OF HEAT CONDUCTING MATERIAL ADAPTED TO BE OPERATIVELY FITTED INTO A CYLINDER OF THE ENGINE AND CARRYING A GROUNDING ELECTRODE, AN INSULATING CORE WITHIN THE SHELL, A CONDUCTOR WITHIN SAID CORE CARRYING AN ELECTRODE ADAPTED TO FORM A SPARK GAP BETWEEN IT AND THE GROUNDING ELECTRODE, AND A SOLID HEAT CONDUCTIVE ELEMENT IN THE FORM OF A CUP SHAPED SLEEVE SURROUNDING THE CORE AND SEATED WITHIN BUT OUT OF CONTACT WITH THE UPPER PORTION OF THE SHELL TO LEAVE AN AIR SPACE BETWEEN ITS SIDE WALL AND THE SHELL, THE SAID ELEMENT BEING COMPOSED OF A SUBSTANCE THAT IS DISTORTABLE BY TEMPERATURE AND THE SIDE WALL OF WHICH IS ADAPTED TO BEND OUTWARD LATERALLY INTO THERMAL CONTACT WITH THE SHELL UPON RISE IN TEMPERATURE ABOVE A PREDETERMINED DEGREE AND RETURN TO ITS ORIGINAL FORM OUT OF CONTACT WITH THE SHELL UPON FALL BELOW SAID DEGREE THUS INCREASING AND DECREASING THE CAPACITY OF THE SHELL FOR DISSIPATING HEAT OF COMBUSTION. 